A depressed mood seems to preferentially influence the right hemisphere's electrophysiological activity and attentional function. Given the importance of right hemisphere function in human emotion, a better understanding of this phenomenon could help integrate biological and psychological approaches to depression. In this research, we examine how depression influences the EEG and ERP recorded as the subject performs elementary attentional processes that can be related to specific neuropsychological mechanisms. Experiment 1 examines visual orienting mechanisms that can be related to parietal lobe contributions to attention. Experiment 2 examines auditory attentional processes that have been shown to be influenced by depression and that have proved useful in research on the role of the frontal lobes in attention. Both experiments are repeated in three studies: the first uses mood induction to contrast a depressed with a neutral mood in normals, the second examines students who report high levels of depression, and the third examines clinically depressed subjects. By developing sensitive measures of the right hemisphere's attentional capacity in depression, it may be possible to study a model system that clarifies how depressive affect simultaneously regulates neural and cognitive function.